Test two objects for inequality.
true if !(this == that), false otherwise.
Equivalent to x.hashCode except for boxed numeric types and null. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For null returns a hashcode where null.hashCode throws a NullPointerException.
a hash value consistent with ==
Alias for concat
The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).
true if the receiver object is equivalent to the argument; false otherwise.
Appends all elements of this view to a string builder. The written text consists of the string representations (w.r.t. the method toString) of all elements of this view without any separator string.
Example:
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = new StringBuilder() b: StringBuilder = scala> val h = a.addString(b) h: StringBuilder = 1234
the string builder to which elements are appended.
the string builder b to which elements were appended.
Appends all elements of this view to a string builder using a separator string. The written text consists of the string representations (w.r.t. the method toString) of all elements of this view, separated by the string sep.
Example:
scala> val a = List(1,2,3,4) a: List[Int] = List(1, 2, 3, 4) scala> val b = new StringBuilder() b: StringBuilder = scala> a.addString(b, ", ") res0: StringBuilder = 1, 2, 3, 4
the string builder to which elements are appended.
the separator string.
the string builder b to which elements were appended.
Appends all elements of this view to a string builder using start, end, and separator strings. The written text begins with the string start and ends with the string end. Inside, the string representations (w.r.t. the method toString) of all elements of this view are separated by the string sep.
Example:
scala> val a = List(1,2,3,4)
a: List[Int] = List(1, 2, 3, 4)
scala> val b = new StringBuilder()
b: StringBuilder =
scala> a.addString(b , "List(" , ", " , ")")
res5: StringBuilder = List(1, 2, 3, 4)
the string builder to which elements are appended.
the starting string.
the separator string.
the ending string.
the string builder b to which elements were appended.
Cast the receiver object to be of type T0.
Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.
the receiver object.
ClassCastException if the receiver object is not an instance of the erasure of type T0.
Create a copy of the receiver object.
The default implementation of the clone method is platform dependent.
a copy of the receiver object.
Builds a new view by applying a partial function to all elements of this view on which the function is defined.
the element type of the returned view.
the partial function which filters and maps the view.
a new view resulting from applying the given partial function pf to each element on which it is defined and collecting the results. The order of the elements is preserved.
Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.
Finds the first element of the view for which the given partial function is defined, and applies the partial function to it.
Note: may not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the partial function
an option value containing pf applied to the first value for which it is defined, or None if none exists.
Seq("a", 1, 5L).collectFirst({ case x: Int => x*10 }) = Some(10)
Returns a new view containing the elements from the left hand operand followed by the elements from the right hand operand. The element type of the view is the most specific superclass encompassing the element types of the two operands.
the element type of the returned collection.
the traversable to append.
a new view which contains all elements of this view followed by all elements of suffix.
Copy elements to an array, returning the number of elements written.
Fills the given array xs starting at index start with at most len elements of this view.
Copying will stop once either all the elements of this view have been copied, or the end of the array is reached, or len elements have been copied.
the type of the elements of the array.
the array to fill.
the starting index of xs.
the maximal number of elements to copy.
the number of elements written to the array
Reuse: After calling this method, one should discard the iterator it was called on. Using it is undefined and subject to change. Note: will not terminate for infinite-sized collections.
Copy elements to an array, returning the number of elements written.
Fills the given array xs starting at index start with values of this view.
Copying will stop once either all the elements of this view have been copied, or the end of the array is reached.
the type of the elements of the array.
the array to fill.
the starting index of xs.
the number of elements written to the array Note: will not terminate for infinite-sized collections.
Copy elements to an array, returning the number of elements written.
Fills the given array xs starting at index start with values of this view.
Copying will stop once either all the elements of this view have been copied, or the end of the array is reached.
the type of the elements of the array.
the array to fill.
the number of elements written to the array Note: will not terminate for infinite-sized collections.
Tests whether every element of this collection's iterator relates to the corresponding element of another collection by satisfying a test predicate.
the type of the elements of that
the other collection
the test predicate, which relates elements from both collections
true if both collections have the same length and p(x, y) is true for all corresponding elements x of this iterator and y of that, otherwise false
Counts the number of elements in the view which satisfy a predicate.
the predicate used to test elements.
the number of elements satisfying the predicate p.
Selects all elements except first n ones.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the number of elements to drop from this view.
a view consisting of all elements of this view except the first n ones, or else the empty view, if this view has less than n elements. If n is negative, don't drop any elements.
Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.
Selects all elements except last n ones.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the number of elements to drop from this view.
a view consisting of all elements of this view except the last n ones, or else the empty view, if this view has less than n elements. If n is negative, don't drop any elements.
Drops longest prefix of elements that satisfy a predicate.
Note: might return different results for different runs, unless the underlying collection type is ordered.
The predicate used to test elements.
the longest suffix of this view whose first element does not satisfy the predicate p.
Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.
The empty iterable of the same type as this iterable
an empty iterable of type C.
Tests whether the argument (that) is a reference to the receiver object (this).
The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:
x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
null.eq(null) returns true. When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).
true if the argument is a reference to the receiver object; false otherwise.
The equality method for reference types. Default implementation delegates to eq.
See also equals in scala.Any.
true if the receiver object is equivalent to the argument; false otherwise.
Selects all elements of this view which do not satisfy a predicate.
the predicate used to test elements.
a new view consisting of all elements of this view that do not satisfy the given predicate pred. Their order may not be preserved.
Called by the garbage collector on the receiver object when there are no more references to the object.
The details of when and if the finalize method is invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.
Finds the first element of the view satisfying a predicate, if any.
Note: may not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the predicate used to test elements.
an option value containing the first element in the view that satisfies p, or None if none exists.
Converts this view of traversable collections into a view formed by the elements of these traversable collections.
The resulting collection's type will be guided by the type of view. For example:
val xs = List(
Set(1, 2, 3),
Set(1, 2, 3)
).flatten
// xs == List(1, 2, 3, 1, 2, 3)
val ys = Set(
List(1, 2, 3),
List(3, 2, 1)
).flatten
// ys == Set(1, 2, 3)
the type of the elements of each traversable collection.
an implicit conversion which asserts that the element type of this view is a GenTraversable.
a new view resulting from concatenating all element views.
Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.
Folds the elements of this view using the specified associative binary operator. The default implementation in IterableOnce is equivalent to foldLeft but may be overridden for more efficient traversal orders.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
Note: will not terminate for infinite-sized collections.
a type parameter for the binary operator, a supertype of A.
a neutral element for the fold operation; may be added to the result an arbitrary number of times, and must not change the result (e.g., Nil for list concatenation, 0 for addition, or 1 for multiplication).
a binary operator that must be associative.
the result of applying the fold operator op between all the elements and z, or z if this view is empty.
Applies a binary operator to a start value and all elements of this view, going left to right.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
the result type of the binary operator.
the start value.
the binary operator.
the result of inserting op between consecutive elements of this view, going left to right with the start value z on the left:
op(...op(z, x_1), x_2, ..., x_n)
where x1, ..., xn are the elements of this view. Returns z if this view is empty.
Applies a binary operator to all elements of this view and a start value, going right to left.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
the result type of the binary operator.
the start value.
the binary operator.
the result of inserting op between consecutive elements of this view, going right to left with the start value z on the right:
op(x_1, op(x_2, ... op(x_n, z)...))
where x1, ..., xn are the elements of this view. Returns z if this view is empty.
Returns string formatted according to given format string. Format strings are as for String.format (@see java.lang.String.format).
Returns the runtime class representation of the object.
a class object corresponding to the runtime type of the receiver.
Partitions this view into a map of views according to some discriminator function.
Note: Even when applied to a view or a lazy collection it will always force the elements.
the type of keys returned by the discriminator function.
the discriminator function.
A map from keys to views such that the following invariant holds:
(xs groupBy f)(k) = xs filter (x => f(x) == k)
That is, every key k is bound to a view of those elements x for which f(x) equals k.
Partitions this view into a map of views according to a discriminator function key. Each element in a group is transformed into a value of type B using the value function.
It is equivalent to groupBy(key).mapValues(_.map(f)), but more efficient.
case class User(name: String, age: Int) def namesByAge(users: Seq[User]): Map[Int, Seq[String]] = users.groupMap(_.age)(_.name)
Note: Even when applied to a view or a lazy collection it will always force the elements.
the type of keys returned by the discriminator function
the type of values returned by the transformation function
the discriminator function
the element transformation function
Partitions this view into a map according to a discriminator function key. All the values that have the same discriminator are then transformed by the value function and then reduced into a single value with the reduce function.
It is equivalent to groupBy(key).mapValues(_.map(f).reduce(reduce)), but more efficient.
def occurrences[A](as: Seq[A]): Map[A, Int] = as.groupMapReduce(identity)(_ => 1)(_ + _)
Note: Even when applied to a view or a lazy collection it will always force the elements.
Partitions elements in fixed size views.
the number of elements per group
An iterator producing views of size size, except the last will be less than size size if the elements don't divide evenly.
scala.collection.Iterator, method grouped
The hashCode method for reference types. See hashCode in scala.Any.
the hash code value for this object.
Selects the first element of this view.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the first element of this view.
NoSuchElementException if the view is empty.
Optionally selects the first element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the first element of this view if it is nonempty, None if it is empty.
The initial part of the collection without its last element.
Note: Even when applied to a view or a lazy collection it will always force the elements.
Iterates over the inits of this view. The first value will be this view and the final one will be an empty view, with the intervening values the results of successive applications of init.
Note: Even when applied to a view or a lazy collection it will always force the elements.
an iterator over all the inits of this view
List(1,2,3).inits = Iterator(List(1,2,3), List(1,2), List(1), Nil)
Tests whether the view is empty.
Note: Implementations in subclasses that are not repeatedly traversable must take care not to consume any elements when isEmpty is called.
true if the view contains no elements, false otherwise.
Test whether the dynamic type of the receiver object is T0.
Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will return true. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.
true if the receiver object is an instance of erasure of type T0; false otherwise.
Tests whether this view can be repeatedly traversed. Always true for Iterables and false for Iterators unless overridden.
true if it is repeatedly traversable, false otherwise.
The companion object of this view, providing various factory methods.
When implementing a custom collection type and refining CC to the new type, this method needs to be overridden to return a factory for the new type (the compiler will issue an error otherwise).
Iterator can be used only once
The number of elements in this view, if it can be cheaply computed, -1 otherwise. Cheaply usually means: Not requiring a collection traversal.
Selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
The last element of this view.
NoSuchElementException If the view is empty.
Optionally selects the last element.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the last element of this view$ if it is nonempty, None if it is empty.
Zips that iterable collection with an existing LazyZip2. The elements in each collection are not consumed until a strict operation is invoked on the returned LazyZip3 decorator.
the type of the third element in each eventual triple
the iterable providing the third element of each eventual triple
a decorator LazyZip3 that allows strict operations to be performed on the lazily evaluated tuples or chained calls to lazyZip. Implicit conversion to Iterable[(El1, El2, B)] is also supported.
Finds the largest element.
The type over which the ordering is defined.
An ordering to be used for comparing elements.
the largest element of this view with respect to the ordering ord.
UnsupportedOperationException if this view is empty.
Finds the first element which yields the largest value measured by function f.
The result type of the function f.
The measuring function.
An ordering to be used for comparing elements.
the first element of this view with the largest value measured by function f with respect to the ordering cmp.
UnsupportedOperationException if this view is empty.
Finds the first element which yields the largest value measured by function f.
The result type of the function f.
The measuring function.
An ordering to be used for comparing elements.
an option value containing the first element of this view with the largest value measured by function f with respect to the ordering cmp.
Finds the largest element.
The type over which the ordering is defined.
An ordering to be used for comparing elements.
an option value containing the largest element of this view with respect to the ordering ord.
Finds the smallest element.
The type over which the ordering is defined.
An ordering to be used for comparing elements.
the smallest element of this view with respect to the ordering ord.
UnsupportedOperationException if this view is empty.
Finds the first element which yields the smallest value measured by function f.
The result type of the function f.
The measuring function.
An ordering to be used for comparing elements.
the first element of this view with the smallest value measured by function f with respect to the ordering cmp.
UnsupportedOperationException if this view is empty.
Finds the first element which yields the smallest value measured by function f.
The result type of the function f.
The measuring function.
An ordering to be used for comparing elements.
an option value containing the first element of this view with the smallest value measured by function f with respect to the ordering cmp.
Finds the smallest element.
The type over which the ordering is defined.
An ordering to be used for comparing elements.
an option value containing the smallest element of this view with respect to the ordering ord.
Displays all elements of this view in a string.
Delegates to addString, which can be overridden.
a string representation of this view. In the resulting string the string representations (w.r.t. the method toString) of all elements of this view follow each other without any separator string.
Displays all elements of this view in a string using a separator string.
Delegates to addString, which can be overridden.
the separator string.
a string representation of this view. In the resulting string the string representations (w.r.t. the method toString) of all elements of this view are separated by the string sep.
List(1, 2, 3).mkString("|") = "1|2|3"
Displays all elements of this view in a string using start, end, and separator strings.
Delegates to addString, which can be overridden.
the starting string.
the separator string.
the ending string.
a string representation of this view. The resulting string begins with the string start and ends with the string end. Inside, the string representations (w.r.t. the method toString) of all elements of this view are separated by the string sep.
List(1, 2, 3).mkString("(", "; ", ")") = "(1; 2; 3)"
Equivalent to !(this eq that).
true if the argument is not a reference to the receiver object; false otherwise.
Tests whether the view is not empty.
true if the view contains at least one element, false otherwise.
Wakes up a single thread that is waiting on the receiver object's monitor.
not specified by SLS as a member of AnyRef
Wakes up all threads that are waiting on the receiver object's monitor.
not specified by SLS as a member of AnyRef
A pair of, first, all elements that satisfy predicate p and, second, all elements that do not. Interesting because it splits a collection in two.
The default implementation provided here needs to traverse the collection twice. Strict collections have an overridden version of partition in StrictOptimizedIterableOps, which requires only a single traversal.
Applies a function f to each element of the view and returns a pair of views: the first one made of those values returned by f that were wrapped in scala.util.Left, and the second one made of those wrapped in scala.util.Right.
Example:
val xs = `View`(1, "one", 2, "two", 3, "three") partitionMap {
case i: Int => Left(i)
case s: String => Right(s)
}
// xs == (`View`(1, 2, 3),
// `View`(one, two, three))
the element type of the first resulting collection
the element type of the second resulting collection
the 'split function' mapping the elements of this view to an scala.util.Either
a pair of views: the first one made of those values returned by f that were wrapped in scala.util.Left, and the second one made of those wrapped in scala.util.Right.
Multiplies up the elements of this collection.
the result type of the * operator.
an implicit parameter defining a set of numeric operations which includes the * operator to be used in forming the product.
the product of all elements of this view with respect to the * operator in num.
Reduces the elements of this view using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
A type parameter for the binary operator, a supertype of A.
A binary operator that must be associative.
The result of applying reduce operator op between all the elements if the view is nonempty.
UnsupportedOperationException if this view is empty.
Applies a binary operator to all elements of this view, going left to right.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
the result type of the binary operator.
the binary operator.
the result of inserting op between consecutive elements of this view, going left to right:
op( op( ... op(x_1, x_2) ..., x_{n-1}), x_n)
where x1, ..., xn are the elements of this view.
UnsupportedOperationException if this view is empty.
Optionally applies a binary operator to all elements of this view, going left to right.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
the result type of the binary operator.
the binary operator.
an option value containing the result of reduceLeft(op) if this view is nonempty, None otherwise.
Reduces the elements of this view, if any, using the specified associative binary operator.
The order in which operations are performed on elements is unspecified and may be nondeterministic.
A type parameter for the binary operator, a supertype of A.
A binary operator that must be associative.
An option value containing result of applying reduce operator op between all the elements if the collection is nonempty, and None otherwise.
Applies a binary operator to all elements of this view, going right to left.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
the result type of the binary operator.
the binary operator.
the result of inserting op between consecutive elements of this view, going right to left:
op(x_1, op(x_2, ..., op(x_{n-1}, x_n)...))
where x1, ..., xn are the elements of this view.
UnsupportedOperationException if this view is empty.
Optionally applies a binary operator to all elements of this view, going right to left.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered or the operator is associative and commutative.
the result type of the binary operator.
the binary operator.
an option value containing the result of reduceRight(op) if this view is nonempty, None otherwise.
Computes a prefix scan of the elements of the collection.
Note: The neutral element z may be applied more than once.
element type of the resulting collection
neutral element for the operator op
the associative operator for the scan
a new view containing the prefix scan of the elements in this view
Produces a view containing cumulative results of applying the operator going left to right, including the initial value.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the type of the elements in the resulting collection
the initial value
the binary operator applied to the intermediate result and the element
collection with intermediate results
Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.
Produces a collection containing cumulative results of applying the operator going right to left. The head of the collection is the last cumulative result.
Note: will not terminate for infinite-sized collections.
Note: might return different results for different runs, unless the underlying collection type is ordered.
Note: Even when applied to a view or a lazy collection it will always force the elements.
Example:
List(1, 2, 3, 4).scanRight(0)(_ + _) == List(10, 9, 7, 4, 0)
the type of the elements in the resulting collection
the initial value
the binary operator applied to the intermediate result and the element
collection with intermediate results
The size of this view.
Note: will not terminate for infinite-sized collections.
the number of elements in this view.
Compares the size of this view to the size of another Iterable.
the Iterable whose size is compared with this view's size.
A value x where
x < 0 if this.size < that.size x == 0 if this.size == that.size x > 0 if this.size > that.size
The method as implemented here does not call size directly; its running time is O(this.size min that.size) instead of O(this.size + that.size). The method should be overridden if computing size is cheap and knownSize returns -1.
Compares the size of this view to a test value.
the test value that gets compared with the size.
A value x where
x < 0 if this.size < otherSize x == 0 if this.size == otherSize x > 0 if this.size > otherSize
The method as implemented here does not call size directly; its running time is O(size min otherSize) instead of O(size). The method should be overridden if computing size is cheap and knownSize returns -1.
Returns a value class containing operations for comparing the size of this view to a test value.
These operations are implemented in terms of sizeCompare(Int), and allow the following more readable usages:
this.sizeIs < size // this.sizeCompare(size) < 0 this.sizeIs <= size // this.sizeCompare(size) <= 0 this.sizeIs == size // this.sizeCompare(size) == 0 this.sizeIs != size // this.sizeCompare(size) != 0 this.sizeIs >= size // this.sizeCompare(size) >= 0 this.sizeIs > size // this.sizeCompare(size) > 0
Selects an interval of elements. The returned view is made up of all elements x which satisfy the invariant:
from <= indexOf(x) < until
Note: might return different results for different runs, unless the underlying collection type is ordered.
the lowest index to include from this view.
the lowest index to EXCLUDE from this view.
a view containing the elements greater than or equal to index from extending up to (but not including) index until of this view.
Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.)
the number of elements per group
the distance between the first elements of successive groups
An iterator producing views of size size, except the last element (which may be the only element) will be truncated if there are fewer than size elements remaining to be grouped.
scala.collection.Iterator, method sliding
Groups elements in fixed size blocks by passing a "sliding window" over them (as opposed to partitioning them, as is done in grouped.) The "sliding window" step is set to one.
the number of elements per group
An iterator producing views of size size, except the last element (which may be the only element) will be truncated if there are fewer than size elements remaining to be grouped.
scala.collection.Iterator, method sliding
Splits this view into a prefix/suffix pair according to a predicate.
Note: c span p is equivalent to (but possibly more efficient than) (c takeWhile p, c dropWhile p), provided the evaluation of the predicate p does not cause any side-effects.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the test predicate
a pair consisting of the longest prefix of this view whose elements all satisfy p, and the rest of this view.
Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterators that were returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterators as well.
Splits this view into a prefix/suffix pair at a given position.
Note: c splitAt n is equivalent to (but possibly more efficient than) (c take n, c drop n).
Note: might return different results for different runs, unless the underlying collection type is ordered.
the position at which to split.
a pair of views consisting of the first n elements of this view, and the other elements.
Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterators that were returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterators as well.
Returns a Stepper for the elements of this collection.
The Stepper enables creating a Java stream to operate on the collection, see scala.jdk.StreamConverters. For collections holding primitive values, the Stepper can be used as an iterator which doesn't box the elements.
The implicit StepperShape parameter defines the resulting Stepper type according to the element type of this collection.
Int, Short, Byte or Char, an IntStepper is returnedFor collections of Double or Float, a DoubleStepper is returnedFor collections of Long a LongStepper is returnedFor any other element type, an AnyStepper is returnedNote that this method is overridden in subclasses and the return type is refined to S with EfficientSplit, for example IndexedSeqOps.stepper. For Steppers marked with scala.collection.Stepper.EfficientSplit, the converters in scala.jdk.StreamConverters allow creating parallel streams, whereas bare Steppers can be converted only to sequential streams.
Sums up the elements of this collection.
the result type of the + operator.
an implicit parameter defining a set of numeric operations which includes the + operator to be used in forming the sum.
the sum of all elements of this view with respect to the + operator in num.
The rest of the collection without its first element.
Iterates over the tails of this view. The first value will be this view and the final one will be an empty view, with the intervening values the results of successive applications of tail.
an iterator over all the tails of this view
List(1,2,3).tails = Iterator(List(1,2,3), List(2,3), List(3), Nil)
Selects the first n elements.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the number of elements to take from this view.
a view consisting only of the first n elements of this view, or else the whole view, if it has less than n elements. If n is negative, returns an empty view.
Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.
Selects the last n elements.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the number of elements to take from this view.
a view consisting only of the last n elements of this view, or else the whole view, if it has less than n elements. If n is negative, returns an empty view.
Takes longest prefix of elements that satisfy a predicate.
Note: might return different results for different runs, unless the underlying collection type is ordered.
The predicate used to test elements.
the longest prefix of this view whose elements all satisfy the predicate p.
Applies a side-effecting function to each element in this collection. Strict collections will apply f to their elements immediately, while lazy collections like Views and LazyLists will only apply f on each element if and when that element is evaluated, and each time that element is evaluated.
the return type of f
a function to apply to each element in this view
The same logical collection as this
Given a collection factory factory, convert this collection to the appropriate representation for the current element type A. Example uses:
xs.to(List) xs.to(ArrayBuffer) xs.to(BitSet) // for xs: Iterable[Int]
Convert collection to array.
This collection as an Iterable[A]. No new collection will be built if this is already an Iterable[A].
This collection as a Seq[A]. This is equivalent to to(Seq) but might be faster.
Creates a String representation of this object. The default representation is platform dependent. On the java platform it is the concatenation of the class name, "@", and the object's hashcode in hexadecimal.
a String representation of the object.
Transposes this view of iterable collections into a view of views.
The resulting collection's type will be guided by the static type of view. For example:
val xs = List(
Set(1, 2, 3),
Set(4, 5, 6)).transpose
// xs == List(
// List(1, 4),
// List(2, 5),
// List(3, 6))
val ys = Vector(
List(1, 2, 3),
List(4, 5, 6)).transpose
// ys == Vector(
// Vector(1, 4),
// Vector(2, 5),
// Vector(3, 6))
Note: Even when applied to a view or a lazy collection it will always force the elements.
the type of the elements of each iterable collection.
an implicit conversion which asserts that the element type of this view is an Iterable.
a two-dimensional view of views which has as nth row the nth column of this view.
IllegalArgumentException if all collections in this view are not of the same size.
Converts this view of pairs into two collections of the first and second half of each pair.
val xs = `View`(
(1, "one"),
(2, "two"),
(3, "three")).unzip
// xs == (`View`(1, 2, 3),
// `View`(one, two, three))
the type of the first half of the element pairs
the type of the second half of the element pairs
an implicit conversion which asserts that the element type of this view is a pair.
a pair of views, containing the first, respectively second half of each element pair of this view.
Converts this view of triples into three collections of the first, second, and third element of each triple.
val xs = `View`(
(1, "one", '1'),
(2, "two", '2'),
(3, "three", '3')).unzip3
// xs == (`View`(1, 2, 3),
// `View`(one, two, three),
// `View`(1, 2, 3))
the type of the first member of the element triples
the type of the second member of the element triples
the type of the third member of the element triples
an implicit conversion which asserts that the element type of this view is a triple.
a triple of views, containing the first, second, respectively third member of each element triple of this view.
A view over the elements of this collection.
Creates a non-strict filter of this view.
Note: the difference between c filter p and c withFilter p is that the former creates a new collection, whereas the latter only restricts the domain of subsequent map, flatMap, foreach, and withFilter operations.
Note: might return different results for different runs, unless the underlying collection type is ordered.
the predicate used to test elements.
an object of class WithFilter, which supports map, flatMap, foreach, and withFilter operations. All these operations apply to those elements of this view which satisfy the predicate p.
Returns a view formed from this view and another iterable collection by combining corresponding elements in pairs. If one of the two collections is longer than the other, its remaining elements are ignored.
the type of the second half of the returned pairs
The iterable providing the second half of each result pair
a new view containing pairs consisting of corresponding elements of this view and that. The length of the returned collection is the minimum of the lengths of this view and that.
Returns a view formed from this view and another iterable collection by combining corresponding elements in pairs. If one of the two collections is shorter than the other, placeholder elements are used to extend the shorter collection to the length of the longer.
the iterable providing the second half of each result pair
the element to be used to fill up the result if this view is shorter than that.
the element to be used to fill up the result if that is shorter than this view.
a new collection of type That containing pairs consisting of corresponding elements of this view and that. The length of the returned collection is the maximum of the lengths of this view and that. If this view is shorter than that, thisElem values are used to pad the result. If that is shorter than this view, thatElem values are used to pad the result.
Zips this view with its indices.
A new view containing pairs consisting of all elements of this view paired with their index. Indices start at 0.
List("a", "b", "c").zipWithIndex == List(("a", 0), ("b", 1), ("c", 2))
Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.
Tests whether a predicate holds for at least one element of this view.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
true if the given predicate p is satisfied by at least one element of this view, otherwise false
(lazyZip2: View[(El1, El2)]).exists(p)
Selects all elements of this view which satisfy a predicate.
a new iterator consisting of all elements of this view that satisfy the given predicate p. The order of the elements is preserved.
(lazyZip2: View[(El1, El2)]).filter(pred)
Builds a new view by applying a function to all elements of this view and using the elements of the resulting collections.
For example:
def getWords(lines: Seq[String]): Seq[String] = lines flatMap (line => line split "\\W+")
The type of the resulting collection is guided by the static type of view. This might cause unexpected results sometimes. For example:
// lettersOf will return a Seq[Char] of likely repeated letters, instead of a Set
def lettersOf(words: Seq[String]) = words flatMap (word => word.toSet)
// lettersOf will return a Set[Char], not a Seq
def lettersOf(words: Seq[String]) = words.toSet flatMap ((word: String) => word.toSeq)
// xs will be an Iterable[Int]
val xs = Map("a" -> List(11,111), "b" -> List(22,222)).flatMap(_._2)
// ys will be a Map[Int, Int]
val ys = Map("a" -> List(1 -> 11,1 -> 111), "b" -> List(2 -> 22,2 -> 222)).flatMap(_._2)
the element type of the returned collection.
the function to apply to each element.
a new view resulting from applying the given collection-valued function f to each element of this view and concatenating the results.
(lazyZip2: View[(El1, El2)]).flatMap(f)
Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.
Tests whether a predicate holds for all elements of this view.
Note: may not terminate for infinite-sized collections.
the predicate used to test elements.
true if this view is empty or the given predicate p holds for all elements of this view, otherwise false.
(lazyZip2: View[(El1, El2)]).forall(p)
Apply f to each element for its side effects Note: [U] parameter needed to help scalac's type inference.
(lazyZip2: View[(El1, El2)]).foreach(f)
Analogous to zip except that the elements in each collection are not consumed until a strict operation is invoked on the returned LazyZip2 decorator.
Calls to lazyZip can be chained to support higher arities (up to 4) without incurring the expense of constructing and deconstructing intermediary tuples.
val xs = List(1, 2, 3) val res = (xs lazyZip xs lazyZip xs lazyZip xs).map((a, b, c, d) => a + b + c + d) // res == List(4, 8, 12)
the type of the second element in each eventual pair
a decorator LazyZip2 that allows strict operations to be performed on the lazily evaluated pairs or chained calls to lazyZip. Implicit conversion to Iterable[(A, B)] is also supported.
(lazyZip2: View[(El1, El2)]).lazyZip
Builds a new view by applying a function to all elements of this view.
the element type of the returned view.
the function to apply to each element.
a new view resulting from applying the given function f to each element of this view and collecting the results.
(lazyZip2: View[(El1, El2)]).map(f)
Reuse: After calling this method, one should discard the iterator it was called on, and use only the iterator that was returned. Using the old iterator is undefined, subject to change, and may result in changes to the new iterator as well.
Converts this view to a string.
a string representation of this collection. By default this string consists of the className of this view, followed by all elements separated by commas and enclosed in parentheses.
(lazyZip2: View[(El1, El2)]).toString()
© 2002-2019 EPFL, with contributions from Lightbend.
Licensed under the Apache License, Version 2.0.
https://www.scala-lang.org/api/2.13.0/scala/collection/LazyZip2.html
Decorator representing lazily zipped pairs.